A semiautomatic, centerfire rifle that has the capacity to accept a detachable magazine and any one of the following:A pistol grip that protrudes conspicuously beneath the action of the weapon.
A thumbhole stock.
A folding or telescoping stock.
A grenade launcher or flare launcher.
A flash suppressor.
A forward pistol grip.
A semiautomatic, centerfire rifle that has a fixed magazine with the capacity to accept more than 10 rounds.
A semiautomatic, centerfire rifle that has an overall length of less than 30 inches.

So if you have a typical over-the-counter BB-AR, you need to do the following:

Remove flash hider - replace with a real muzzlebrake or compensator or nothing (i opted for thread protector, which is pretty much nothing) check here for risk factors: https://sites.google.com/site/featur...muzzle-devices
Fixed stock - get an A2 stock or similar fixed stock, or pin your adjustable stock to become fixed.
Remove pistol grip - replace with Hammerhead, monsterman, solar tactical, home made grip fin etc. I opted to the hammerhead because it has a letter to the DOJ saying its not a PG.
Remove Forward Pistol Grip if you have one, and any other features in bold.